Pre-cast concrete piles are now usually of the jointed type, unless a large contract with a more or less constant depth of piling makes it economical to pre-cast the piles on site, thus overcoming a potential difficulty in transport.

Pre-cast non-jointed piles are generally of square section and may be up to 600×600mm to work at loads up to approximetely 3000kN in suitable ground. Typical sizes and capacities are given in
Table 3.1.

Extending pre-cast piles that do not have pre-formed joints is a lengthy process, involving breaking down the projecting pile head to provide a suitable lap for the steel and casting concrete to form a joining surface.

The pile sections are then butted together in a steel sleeve using an epoxy cement, or joined by inserting steel dowel bars into drilled holes and using an epoxy cement to fix them in place.

Good alignment of the pile sections is required to prevent excessive bending stresses developing on subsequent re-driving.

There are some benefits from pre-stressing concrete piles. Tensile stresses which can be set up in a pile during driving are better resisted, and the pile is less likely to be damaged during handling in the casting yard and when being pitched.

Bending stresses which can occur during driving are also less likely to produce cracking. However, the ultimate strength in axial compression is decreased as the level of pre-stress is increased, and pre-stressed piles are therefore more vulnerable to damage from striking obstructions during driving.

They are also difficult to shorten and special techniques have to be employed. As a result they are most suitable for a constant-length application.

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